Capstan or low tension or drum spiral conveyors have been utilized in numerous industries for many years. Illustrated in FIG. 1 is a schematic diagram of a drum spiral conveyor 2, which is representative of those found in the prior art. The drum spiral conveyor 2 elevates or lowers items that rest on a conveyor belt that progress in a helical path around a drum. The conveyor belt is a closed loop that circulates up or down the drum over a conveyer bed that coils around the drum. The drum is usually driven by a chain that is driven by a gear motor and the belt is usually driven by a gear motor. The belt drive produces belt tension around the drum. The belt to drum frictional contact causes the belt to move up or down the helical slider bed in response to the drum slightly over-driving the belt speed. If the belt speed decreases relative to the drum speed, the belt may become slack on the drum thereby reducing the drum belt driving force. In contrast, an increase in the belt speed relative to the drum speed will increase the belt tension around the drum, which increases the drum belt driving force. As the conveyor belt moves along its path it carries items that rest upon the conveyor belt to a higher or lower level until the items exit the spiral conveyor at the desired destination. A number of operational problems are associated with driving the drum and detecting belt jams on the drum spiral conveyor.